CN105262051B - Transformer excitation flow discrimination method based on sample sequence absolute value partial velocities - Google Patents
Transformer excitation flow discrimination method based on sample sequence absolute value partial velocities Download PDFInfo
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Abstract
The invention discloses a kind of transformer excitation flow discrimination method based on sample sequence absolute value partial velocities, step includes：The difference current of transformer differential protection is sampled with the sample frequency of setting；Calculus of differences is done to sampled data with after the computing that takes absolute value, the sampled data of a newest power frequency period is taken, calculates its coefficient of skew；If the coefficient of skew calculated is more than 0, judge that difference current is excitation surge current；Otherwise, it is determined that difference current is not excitation surge current.The present invention is clear with criterion, and amount of calculation is small, distinguishes substantially, is swift in motion, accurately, low to the hardware requirement of device, is not required to artificial setting valve, realizes the advantages that facilitating.
Description
Technical field
The present invention relates to technical field of transformer relay protection, and in particular to one kind is based on sample sequence absolute value skewness point
The transformer excitation flow discrimination method of cloth.
Background technology
Transformer is highly important electrical equipment in power system, and often capacity is huge for the power transformer in power network,
Involve great expense, it is necessary to which its safe and reliable operation is ensured by protective relaying device.Longitudinal differential protection high sensitivity, selectivity is good,
Frequently as the main protection of transformer in engineering.But the longitudinal differential protection of transformer needs to avoid flowing through differential circuit not
Balanced balanced current.
It is very big that numerical value is likely to occur when voltage recovers after no-load transformer input or Removal of external faults, in differential circuit
Excitation surge current.In some cases, the size of excitation surge current even can be comparable with fault current, transformer longitudinal linked differential protection
It is difficult to avoid this electric current by ratio brake, protection will malfunction.Therefore, excitation surge current is correctly differentiated, to longitudinal differential protection
It is one of key for ensureing tranformer protection action message to carry out accurate braking.
It is main in engineering to prevent excitation surge current from causing differential guarantor using the braking of second harmonic criterion, interval angle locking principle
Shield malfunction.But as power system is fast-developing, long range ultra-high-tension power transmission line serial compensation capacitance and various new idle benefits
Repay device to be widely present, when severe internal failure occurs, resonance may be such that the secondary harmonic component in fault current significantly increases
Greatly, secondary harmonic brake device is easily caused to prevent the correct action of differential protection；The magnetic saturation of modern transformer core material
Point has been greatly reduced, and the second harmonic component of excitation surge current is only at least 7%, and now, second harmonic criterion will be difficult to effectively close
Lock differential protection.In addition, transformer fe core material is updated, novel electric power electric device largely accesses, and can also make specific feelings
Excitation surge current waveform interval angle under condition becomes very little, has had a strong impact on the reliability of interval angle blocking method.
In view of the above-mentioned problems, expert, scholars conduct extensive research, and propose many new excitation surge current mirror
Other method.But these method species are various, different properties are perfect not enough in theory, need practice test in performance.Example
Such as, inductance parameters method of identification, magnetic flux characteristic method etc., clear principle, excellent effect, but information of voltage need to be obtained, make protection hardware
Configuration is complicated, and is easily influenceed and out of service by voltage transformer saturation or secondary circuit broken string；Wavelet analysis method, waveform point
Cloth characteristic method etc., excitation surge current and fault current can be correctly distinguished only in accordance with current waveform information, but high is required to sample rate,
To the complex disposal process of data, it is unfavorable for field device realization；Integral area compares method identification excitation surge current, possesses calculating letter
Singly, the advantages of not influenceed by higher hamonic wave, but the transformer input moment need to be calculated, and the calculation error for putting into the moment easily causes
Method fails.
In fact, after the sampled data of transformer excitation flow and non-excitation surge current takes absolute value, its numeric distribution is present
Very big difference：
(1) the non-excitation surge current (internal fault current, external fault electric current, load current etc.) of transformer is sinusoidal signal
Or quasi sine signal, its derivative are cosine function, so, its derivative is zero at crest, and its derivative reaches most at zero crossing
Greatly, and derivative is slowly varying with signal waveform.It is seen that near sine curve crest, derivative is smaller, sampling point distributions
It is more dense；And sine curve near zero-crossing point, derivative are larger, sampling point distributions are more sparse.It is sinusoidal as shown in Fig. 2 (a)
After (or quasi sine) current signal waveform sampled data takes absolute value, the dense area of its numeric distribution is located at numeric distribution rarefaction
Top, in negative skewness.Transformer differential current sampled with specified sample frequency, takes 1 power frequency period (i.e.
0.02 second) in sampled data analyzed, handled, according to partial velocities coefficient formulas calculate partial velocities coefficient it is small
In 0.
(2) excitation surge current waveform has a variety of notable features, all affects the distribution of sampled point.Interruption corner characteristics will make sampling
Point data is very dense in interval angle punishment cloth；Inrush also tends to be inclined to the side of time shaft, makes waveform close to the time
Change slowly at axle, form the dense distributed area of another sampled point.In addition, shove with pinnacle wave characteristic, although in crest
It is also zero to locate derivative, but because it is peaked wave, derivative drastically changes, and sampled point also can be more sparse；Can also in terms of mechanism
It is confirmed, because the peaked wave that shoves is to be conducted by sinusoidal signal through non-linear exciter curve after all, and excitation
Slope becomes very little after curve crosses flex point, forms the peaked wave to shove, so sampled point can regard sinusoidal letter as at the peaked wave that shoves
Scattered (or dilution) of number sampled point, shove signal at peaked wave sampling point distributions naturally than sparse.As shown in Fig. 2 (b),
After transformer excitation flow signal waveform sampled data takes absolute value, the dense area of its numeric distribution is located at numeric distribution rarefaction
Lower section, in positive skewness.The sampled data in 1 power frequency period of difference current is taken to be analyzed, handled, according to partial velocities coefficient
The partial velocities coefficient that calculation formula calculates is more than 0.
In a word, the partial velocities coefficient of the sampled data absolute value of transformer excitation flow and non-excitation surge current is respectively greater than
With less than zero, significant difference, can be encouraged using the symbol of the partial velocities coefficient of difference current sampled data absolute value to differentiate
Magnetic shoves and non-excitation surge current (fault current etc.).
Based on above-mentioned principle, this patent proposes that the transformer excitation flow based on sample sequence absolute value partial velocities differentiates
Method, transformer excitation flow and other electric currents can effectively be differentiated using this method, ensure the reliable of transformer differential protection
Property.
The content of the invention
It is an object of the invention to：In view of the shortcomings of the prior art with deficiency, there is provided a kind of criterion is clear, distinguish it is obvious,
Differentiate that accuracy is high, highly reliable, low to the hardware requirement of device, it is not necessary to artificial setting valve, realize easily based on sampling
The transformer excitation flow discrimination method of sequence absolute value partial velocities.
The present invention is achieved through the following technical solutions：
A kind of transformer excitation flow discrimination method based on sample sequence absolute value partial velocities, comprises the following steps：
Step 1：With the sample frequency f of settings=50N hertz, N are positive integer, to the differential electricity of transformer differential protection
Stream x (t) is sampled, and obtains the sampled value sequence { x (i) } of difference current, i is positive integer；
Step 2：Calculus of differences is carried out to the sampled value sequence { x (i) } of difference current, obtains the sampling value difference of difference current
Sub-sequence { y (i) }, i are positive integer；
Step 3：The each element of the sampled value difference sequence { y (i) } of difference current is taken absolute value, forms sample data sequence
Arrange { z (i) }, i is positive integer；
Step 4：Calculate the partial velocities coefficient S of newest N number of element of sample data sequence { z (i) }；
Step 5：If the partial velocities coefficient S of newest N number of element of the sample data sequence { z (i) } calculated is more than
0, then the difference current for judging current transformer differential protection is excitation surge current；Otherwise, it is determined that current transformer differential protection
Difference current is not excitation surge current.
Preferably, N is the sampling number of difference current in power frequency period in the step 1, N takes more than or equal to 24,
Integer value less than or equal to 100.
Preferably, the sampled value difference sequence { y (i) } of the difference current in the step 2 is calculated by formula (1) and obtained：
Y (i)=x (i)-x (i-b) (1)
In formula (1), i is positive integer；Y (i) is i-th of element of the sampled value difference sequence { y (i) } of difference current；B=
[N/4], wherein [] is to round symbol；X (i), x (i-b) are respectively i-th yuan of the sampled value sequence { x (i) } of difference current
Element and the i-th-b elements.
Preferably, in the step 4 newest N number of element of sample data sequence { z (i) } partial velocities coefficient S according to
Formula (2) is calculated：
In formula (2), S represents the partial velocities coefficient of newest N number of element of sample data sequence { z (i) }；K represents sample
The sequence number of a newest element in data sequence { z (i) }；Z (i) represents i-th of element of sample data sequence { z (i) }；Table
Show the average value of newest N number of element of sample data sequence { z (i) },Calculation formula such as formula (3) shown in：
In formula (3),Represent the average value of newest N number of element of sample data sequence { z (i) }；K represents sample data sequence
Arrange the sequence number of a newest element in { z (i) }；Z (i) represents i-th of element of sample data sequence { z (i) }.
Transformer excitation flow discrimination method tool of the present invention based on sample sequence absolute value partial velocities has the advantage that：
(1) numerical distribution characteristic of the invention according to the sampled data of transformer differential current, is existed using difference current waveform
The difference of transformer excitation flow state and internal fault status down-sampling sequence absolute value partial velocities coefficient differentiates excitation
Shove.In the case of power transformer interior fault, difference current waveform is sine wave or quasi-sine-wave, and its sample sequence absolute value is inclined
The value of state breadth coefficient is negative；When excitation surge current occurs for transformer, its difference current waveform deviates considerably from sine wave, shows partially
The features such as to time shaft side, interval angle, peaked wave, the value of its sample sequence absolute value partial velocities coefficient is just.The present invention
Differentiating transformer excitation flow and internal fault current using this principle, criterion is clear, distinguishes substantially, discriminating accuracy height,
Reliability is high.
(2) invention is directed to the sampled value sequence of transformer differential current, when deliberately the starting of data is extracted in restriction
To carve, it is not necessary to synchronized sampling, the difference current sampled value for only extracting a newest continuous frequency cycle carry out data processing, because
This excitation surge current differentiates that the time is 1 power frequency period (i.e. 20 milliseconds), judges that the time is short, real-time is good, is advantageous to transformer guarantor
The rapidity of shield, engineering practical value are high.
(3) requirement of the present invention to the a/d converter resolution ratio and sample frequency of protective relaying device be not high；Excitation is gushed
Stream discrimination process amount of calculation is small, and required amount of storage is also smaller.Therefore, implement the inventive method and low is required to hardware unit, simply
Practicality, it is easy to the realization of microcomputer protecting device.
Brief description of the drawings
Fig. 1 is the basic procedure schematic diagram of present invention method.
Fig. 2 (a) and Fig. 2 (b) is respectively excitation surge current and sinusoidal current sample magnitude distribution or accumulation areas in the inventive method
Domain analysis figure.
Fig. 3 is by the simulation model built in the embodiment of the present invention 1.
Fig. 4 (a) and Fig. 4 (b) is respectively the excitation surge current oscillogram and its sample sequence emulated in the embodiment of the present invention 1
Absolute value partial velocities index variation figure.
Fig. 5 (a) and Fig. 5 (b) is respectively the fault current waveform figure and its sample sequence emulated in the embodiment of the present invention 1
Absolute value partial velocities index variation figure.
Embodiment
As shown in figure 1, transformer excitation flow discrimination method of the present embodiment based on sample sequence absolute value partial velocities
The step of include：
Step 1：With the sample frequency f of settings=50N hertz, N are positive integer, to the differential electricity of transformer differential protection
Stream x (t) is sampled, and obtains the sampled value sequence { x (i) } of difference current, i is positive integer；
In the present embodiment, the N is the sampling number of difference current in power frequency period, and N takes more than or equal to 24, is less than
Integer value equal to 100.
Step 2：Calculus of differences is carried out to the sampled value sequence { x (i) } of difference current, obtains the sampling value difference of difference current
Sub-sequence { y (i) }, i are positive integer；
In the present embodiment, the sampled value difference sequence { y (i) } of described difference current is calculated by formula (1) to be obtained：
Y (i)=x (i)-x (i-b) (1)
In formula (1), i is positive integer；Y (i) is i-th of element of the sampled value difference sequence { y (i) } of difference current；B=
[N/4], wherein [] is to round symbol；X (i), x (i-b) are respectively i-th yuan of the sampled value sequence { x (i) } of difference current
Element and the i-th-b elements.
Step 3：The each element of difference current sampled value difference sequence { y (i) } is taken absolute value, forms sample data sequence
{ z (i) }, i are positive integer；
Step 4：Calculate the partial velocities coefficient S of newest N number of element of sample data sequence { z (i) }；
In the present embodiment, the partial velocities coefficient S of newest N number of element of the sample data sequence { z (i) } is according to formula
(2) calculated：
In formula (2), S represents the partial velocities coefficient of newest N number of element of sample data sequence { z (i) }；K represents sample
The sequence number of a newest element in data sequence { z (i) }；Z (i) represents i-th of element of sample data sequence { z (i) }；Table
Show the average value of newest N number of element of sample data sequence { z (i) },Calculation formula such as formula (3) shown in：
In formula (3),Represent the average value of newest N number of element of sample data sequence { z (i) }；K represents sample data sequence
Arrange the sequence number of a newest element in { z (i) }；Z (i) represents i-th of element of sample data sequence { z (i) }.
Step 5：If the partial velocities coefficient S of newest N number of element of the sample data sequence { z (i) } calculated is more than
0, then the difference current for judging current transformer differential protection is excitation surge current；Otherwise, it is determined that current transformer differential protection
Difference current is not excitation surge current.
Referring to 1~step 5 of abovementioned steps, the transformer excitation flow discriminating side based on sample sequence absolute value partial velocities
Method utilizes transformer excitation flow waveform and other non-property electricity that shove according to transformer differential current sample magnitude distribution characteristics
The positive and negative difference of sample sequence absolute value partial velocities coefficient of waveform is flowed, is existed by analyzing, handling transformer differential current signal
Sampled data in one cycle, its partial velocities coefficient is calculated, comes differentiating transformer exciting surge and other electric currents, so as to carry
The performance of high transformer differential protection, clear with criterion, amount of calculation is small, distinguishes substantially, is swift in motion, accurately, to device
Hardware requirement is low, is not required to artificial setting valve, realizes the advantages that facilitating.
The present invention is described in further details below with reference to drawings and examples 1：
Embodiment 1：
Analogue system is built as shown in Figure 3.Three-phase transformer module sets as follows：Connection group is YNd11, rated capacity
60MVA, rated voltage 220kV/110kV, high-low pressure winding resistance 0.02 (pu), leakage inductance 0.08 (pu), saturated core is chosen, is encouraged
Magnetic curve is set to 0,0；0.0024,1.2；1,1.5 (pu).Carry out equivalent left-sided system using three phase mains M, its line voltage is arranged to
220kV, it is 10 ° to set the initial phase angle of A phases, and Infinite bus system can also be used three phase mains to replace.Set respectively at the 20ms moment
Air-drop transformer and AB phase-to phase faults are emulated.By transformer two-sided measurement device, the current information of both sides is obtained, is converted
To after primary side, computing forms difference current, to difference current caused by two kinds of operation conditions emulation respectively such as Fig. 4 (a) and Fig. 5
(a) (for sake of clarity, only analyzed with A phase waveforms).
Step 1：With the sample frequency f of settings=2000 hertz of difference currents to transformer differential protection sample,
Obtain the sampled value sequence of difference current；
Step 2：Calculus of differences is carried out to the sampled value sequence of difference current, obtains the sampled value difference sequence of difference current
Row；
Step 3：The each element of difference current sampled value difference sequence is taken absolute value, forms sample data sequence；
Step 4：The sample data sequence corresponding to 20ms~40ms moment in Fig. 4 (a) and Fig. 5 (a) is taken, is set to sample
Notebook data sequence 1 and sample data sequence 2, calculated according to formula (2) and formula (3), obtain the partial velocities system of sample data sequence 1
Number is 2.7876 × 108, the partial velocities coefficient of sample data sequence 2 is 9.0807 × 1012。
Step 5：Because the partial velocities coefficient of sample data sequence 1 is more than 0, it is possible to determine that electric current is transformation in figure (4)
Device excitation surge current；And the partial velocities coefficient of sample data sequence 2 is less than 0, it is possible to determine that electric current is non-excitation surge current in figure (5)
(fault current, load current etc.).
Fig. 4 (b) and Fig. 5 (b) is real based on the partial velocities coefficient that current waveform calculates in Fig. 4 (a) and Fig. 5 (a) respectively
When change curve.From above it can be seen from the figure that, the coefficient of skew that excitation surge current sampled data is calculated after processing is permanent big
In zero；The coefficient of skew that fault current sampled data is calculated after processing is permanent after of short duration transient process to be less than zero.Checking
More than analyze, it was demonstrated that excitation surge current discrimination method based on sample sequence absolute value partial velocities can effectively differentiate transformation
Device excitation surge current and internal fault current.
The preferred embodiment of the present invention is the foregoing is only, but protection scope of the present invention is not limited to above-mentioned implementation
Example, all technical schemes belonged under thinking of the present invention belong to protection scope of the present invention.It should be pointed out that in the art model
In enclosing, under the premise of not departing from the principle of the invention, retouch, simplify, improve, substitute and combine to what the present invention was done, should all include
Within protection scope of the present invention.
Claims (4)
- A kind of 1. transformer excitation flow discrimination method based on sample sequence absolute value partial velocities, it is characterised in that including Following steps：Step 1：With the sample frequency f of settings=50N hertz, N are positive integer, to the difference current x (t) of transformer differential protection Sampled, obtain the sampled value sequence { x (i) } of difference current, i is positive integer；Step 2：Calculus of differences is carried out to the sampled value sequence { x (i) } of difference current, obtains the sampled value difference sequence of difference current Arrange { y (i) }, i is positive integer；Step 3：The each element of the sampled value difference sequence { y (i) } of difference current is taken absolute value, forms sample data sequence { z (i) }, i is positive integer；Step 4：Calculate the partial velocities coefficient S of newest N number of element of sample data sequence { z (i) }；Step 5：If the partial velocities coefficient S of newest N number of element of the sample data sequence { z (i) } calculated is more than 0, The difference current for judging current transformer differential protection is excitation surge current；Otherwise, it is determined that current transformer differential protection is differential Electric current is not excitation surge current.
- 2. the transformer excitation flow discrimination method according to claim 1 based on sample sequence absolute value partial velocities, Characterized in that, described N is the sampling number of difference current in power frequency period, N takes more than or equal to 24, is less than or equal to 100 integer value.
- 3. the transformer excitation flow discrimination method according to claim 1 based on sample sequence absolute value partial velocities, Obtained characterized in that, the sampled value difference sequence { y (i) } of the difference current in the step 2 is calculated by formula (1)：Y (i)=x (i)-x (i-b) (1)In formula (1), i is positive integer；Y (i) is i-th of element of the sampled value difference sequence { y (i) } of difference current；B=[N/ 4], wherein [] is to round symbol；X (i), x (i-b) be respectively the sampled value sequence { x (i) } of difference current i-th element and I-th-b elements.
- 4. the transformer excitation flow discrimination method according to claim 1 based on sample sequence absolute value partial velocities, Characterized in that, the partial velocities coefficient S of newest N number of element of sample data sequence { z (i) } is according to formula (2) in the step 4 Calculated：<mrow> <mi>S</mi> <mo>=</mo> <munderover> <mo>&Sigma;</mo> <mrow> <mi>i</mi> <mo>=</mo> <mi>k</mi> <mo>-</mo> <mi>N</mi> <mo>+</mo> <mn>1</mn> </mrow> <mi>k</mi> </munderover> <msup> <mrow> <mo>&lsqb;</mo> <mi>z</mi> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> <mo>-</mo> <mover> <mi>z</mi> <mo>&OverBar;</mo> </mover> <mo>&rsqb;</mo> </mrow> <mn>3</mn> </msup> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow>In formula (2), S represents the partial velocities coefficient of newest N number of element of sample data sequence { z (i) }；K represents sample data The sequence number of a newest element in sequence { z (i) }；Z (i) represents i-th of element of sample data sequence { z (i) }；Represent sample The average value of newest N number of element of notebook data sequence { z (i) },Calculation formula such as formula (3) shown in：<mrow> <mover> <mi>z</mi> <mo>&OverBar;</mo> </mover> <mo>=</mo> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mo>&Sigma;</mo> <mrow> <mi>i</mi> <mo>=</mo> <mi>k</mi> <mo>-</mo> <mi>N</mi> <mo>+</mo> <mn>1</mn> </mrow> <mi>k</mi> </munderover> <mi>z</mi> <mrow> <mo>(</mo> <mi>i</mi> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow>In formula (3),Represent the average value of newest N number of element of sample data sequence { z (i) }；K represents sample data sequence { z (i) sequence number of a newest element in }；Z (i) represents i-th of element of sample data sequence { z (i) }.
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| CN107565516B (en) * | 2016-06-30 | 2019-11-08 | 中国电力科学研究院 | A kind of transformer inrush current identification method based on waveform modulated |
| CN106655097B (en) * | 2017-01-09 | 2018-08-17 | 湖南大学 | Power transformer excitation surge current recognition methods |
| CN108847653B (en) * | 2018-07-12 | 2019-11-19 | 广东电网有限责任公司 | A kind of transformer excitation flow recognition method and device based on waveform change rate |
| CN111797143B (en) * | 2020-07-07 | 2023-12-15 | 长沙理工大学 | Aquaculture electricity larceny detection method based on electricity consumption statistical distribution skewness coefficient |
| CN112039021B (en) * | 2020-09-08 | 2022-04-12 | 河南理工大学 | Transformer excitation inrush current identification method based on differential waveform parameters |
| CN113991606B (en) * | 2021-10-18 | 2024-01-02 | 国电南瑞科技股份有限公司 | Excitation surge current misoperation prevention method and device for transformer |
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| CN103683198A (en) * | 2013-12-03 | 2014-03-26 | 昆明理工大学 | Excitation surge current fast identification method based on planar adjacent point distances formed by differential current adjacent order difference |
| CN103675415A (en) * | 2012-08-31 | 2014-03-26 | 西门子公司 | Excitation surge current detection method, excitation surge current brake method and excitation surge current detection device |
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| CN103675415A (en) * | 2012-08-31 | 2014-03-26 | 西门子公司 | Excitation surge current detection method, excitation surge current brake method and excitation surge current detection device |
| CN103683198A (en) * | 2013-12-03 | 2014-03-26 | 昆明理工大学 | Excitation surge current fast identification method based on planar adjacent point distances formed by differential current adjacent order difference |
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